Vl5 



35.2 niilliinol. p. litre spec, t'oml. [)0\ver 0.001952. 



If we lake (i^ for 20° on 0.333, Ostwald'« law of tliliitioii llien 

 yields /= 0.117, which result was \)u{ to the test in a miinbcr of 

 solutions. The acid concentration may now he calculated from the 

 specific conductivity power '). 



The experiments were carried out by rotating a small Mask in 

 the usual manner in a thermostat. The conductivity vessel was 

 furnished with a trebly perforated stopper. Through the stopper was 

 put the plunging electrode, also a little tube leading to the cotton- 

 wool filter and another one to which suction could be applied. 

 Immediately after 11 cc. of the li([uid had been withdrawji the 

 resistance was measured in the usual manner (Wheatstonk bridge, 

 alternating current and telephone) ; 10 cc. were then pipetted off 

 and titrated. 



In Table 2 is found the complete composition of the solutions which 

 are shaken with the two solid phases. We notice that although a 

 totally stationary maximum value was not found, it is very surprising 

 to find how remarkably little anhydride is contained in the solutions 

 which during about two hours still change but httle in composition. 



Hence a large solubility of the anhydride molecules appears but 

 little probable. It is interesting to notice that these solutions contain 

 more phthalic acid than the purely aqueous ones. The solubility ot 

 the acid is thus much promoted by the anhydride present. 



Fig. 2 appears to be the most appropriate one for expressing 

 these results. 



^j As to the neglecting of the influence of the anhydride on the conductivity 

 power see Rivett and Sidgwick (i.e.). 



